I guess the large gap between fighters and healers may be due to the fact that it is easier for fighters to rankwhore than healers. As well as the huge slaughter rate induced by healer trainers.

Another reason of the unbalance is healers inability to utilize their proximus to their advantage, perhaps by running the creatures as they heal Glory. Which devalues some of their ranks, thus making them seem to be lower level in the healer tests. *shrug*